Exhaust gas purification system for hydraulic operating machine

ABSTRACT

When an output value of an exhaust resistance sensor  34  has reached or exceeded a set value ΔPa, a controller  20  executes recovery control of a filter of an exhaust gas purification device  32  after conducting exhaust temperature increasing control by operating a pump discharge pressure increasing device (solenoid proportional valve)  38  so that exhaust gas temperature as an output value of an exhaust temperature sensor  33  reaches a preset value Ta. Thus, the recovery process of the exhaust gas purification device can be executed with reliability by increasing the exhaust gas temperature irrespective of the operating environment and the fuel consumption can be kept at a minimum necessary level.

TECHNICAL FIELD

The present invention relates to an exhaust gas purification system fora hydraulic operating machine. In particular, the invention relates toan exhaust gas purification system for a hydraulic operating machine(e.g., hydraulic shovel) for recovering a filter of an exhaust gaspurification device installed in the hydraulic operating machine bycombusting and removing deposits accumulated on the filter.

BACKGROUND ART

Conventional exhaust gas purification systems for purifying the exhaustgas of a diesel engine include those described in Patent Literatures 1and 2, for example. In the exhaust gas purification system described inthe Patent Literature 1, an exhaust gas purification device including afilter called “particulate filter” (DPF: Diesel Particulate Filter) isplaced in the exhaust system of the engine of a transporting vehicle(e.g., truck) and the amount of particulate matter (hereinafter referredto as “PM”) discharged to the outside is reduced by collecting the PMcontained in the exhaust gas with the filter. In order to prevent theclogging of the PM filter, the exhaust gas purification system executesautomatic recovery control and manual recovery control, for example. Forthe recovery control, an oxidation catalyst is placed upstream of thefilter and the amount of the PM accumulated on the filter (PMaccumulation amount) is estimated by detecting the differential pressureacross the filter. In the automatic recovery control, the temperature ofthe exhaust gas is increased automatically when the PM accumulationamount has exceeded a prescribed value, by which the oxidation catalystis activated and the PM accumulated on the filter is combusted andremoved. In the manual recovery control, when the PM accumulation amounthas exceeded a prescribed value, a warning lamp is lit up so as to urgethe operator to start recovery control by manual operation in a state inwhich the vehicle is stopped. When a manual recovery switch is turned ONby the operator, the temperature of the exhaust gas is increased, bywhich the oxidation catalyst is activated and the PM accumulated on thefilter is combusted and removed.

In the exhaust gas purification system described in the PatentLiterature 2, an exhaust resistance sensor is installed in an exhaustgas processing device of a hydraulic operating machine. For theautomatic recovery control, the degree of the filter clogging isdetected. Before the filter clogging proceeds to a level at whichburnout is caused, a hydraulic load is exerted on the engine bysimultaneously increasing the discharge rate and the discharge pressureof a hydraulic pump. With the increase in the engine load, the outputpower of the engine increases and the exhaust gas temperature rises, bywhich the deposits accumulated on the filter are combusted and thefilter is recovered.

PRIOR ART LITERATURE Patent Literature

-   Patent Literature 1: JP, A 2005-120895-   Patent Literature 2: Japanese Patent No. 3073380

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

For transporting vehicles like trucks, the purification of the exhaustgas is commonly conducted today by installing an exhaust gaspurification device as described in the Patent Literature 1. Also forhydraulic operating machines typified by hydraulic shovels, etc.,exhaust gas regulations (exhaust emission control) are being tightenedstepwise in recent years from the viewpoint of environmentalpreservation and various control technologies related to exhaust gaspurification systems are being discussed as described in the PatentLiterature 2.

In the technique of the Patent Literature 2, the degree of the cloggingis detected by the exhaust resistance sensor installed in the exhaustgas processing device. Before the filter clogging proceeds to the levelat which burnout is caused, the discharge rate and the dischargepressure of the hydraulic pump are simultaneously increased to increasethe engine load and raise the exhaust gas temperature, thereby carryingout the recovery of the filter.

However, the atmospheric temperature changes in a wide range (e.g., −30°C.-40° C.) in the actual operating environment of a hydraulic operatingmachine and the exhaust gas temperature rises accordingly when theatmospheric temperature rises. Therefore, the technique of the PatentLiterature 2 can increase the exhaust gas temperature to an unnecessaryhigh level by the exhaust gas temperature increasing control and consumethe fuel wastefully.

Further, the technique of the Patent Literature 2 specifies that theexhaust gas temperature increasing control is desired to be executed ina non-operating state (in which the operator is not operating themachine/vehicle). In this case, an operation interruption time (duringwhich the operation or work has to be interrupted) becomes necessary.

A first object of the present invention is to provide an exhaust gaspurification system for a hydraulic operating machine that is capable ofexecuting the recovery process of the exhaust gas purification devicewith reliability by increasing the exhaust gas temperature irrespectiveof the operating environment and capable of keeping the fuel consumptionat a minimum necessary level.

A second object of the present invention is to provide an exhaust gaspurification system for a hydraulic operating machine that is capable ofexecuting the recovery process of the exhaust gas purification devicewith reliability by increasing the exhaust gas temperature irrespectiveof the operating environment, capable of keeping the fuel consumption ata minimum necessary level, and capable of reducing the operationinterruption frequency of the machine.

Means for Solving the Problem

(1) In order to achieve the above first object, an invention describedin claim 1 provides an exhaust gas purification system for a hydraulicoperating machine equipped with a diesel engine, an exhaust gaspurification device provided in an exhaust line of the engine, avariable displacement hydraulic pump driven by the engine, a pumpdisplacement adjusting device for controlling the displacement of thehydraulic pump, and at least one hydraulic actuator driven by hydraulicfluid discharged from the hydraulic pump. The exhaust gas purificationsystem comprises: an exhaust resistance sensor for detecting exhaustresistance of the exhaust gas purification device; an exhausttemperature sensor for detecting temperature of exhaust gas in theexhaust gas purification device; a pump discharge pressure increasingdevice provided in a hydraulic line, through which the hydraulic fluiddischarged from the hydraulic pump flows, for increasing dischargepressure of the hydraulic pump; and a recovery control device forexecuting recovery of the exhaust gas purification device by combustingand removing particulate matter accumulated in the exhaust gaspurification device when the exhaust resistance detected by the exhaustresistance sensor has reached or exceeded a set value. The recoverycontrol device includes an exhaust temperature increasing control devicewhich increases the exhaust gas temperature so as to make the exhaustgas temperature detected by the exhaust temperature sensor reach apreset value by increasing absorption torque of the hydraulic pump byoperating at least the latter one (i.e., the pump discharge pressureincreasing device) of the pump displacement adjusting device and thepump discharge pressure increasing device when the exhaust resistancedetected by the exhaust resistance sensor has reached or exceeded theset value.

In the present invention configured as above, when the exhaustresistance detected by the exhaust resistance sensor has reached orexceeded the set value, the exhaust gas temperature is increased so asto make the exhaust gas temperature detected by the exhaust temperaturesensor reach the preset value by operating at least the pump dischargepressure increasing device. Therefore, the recovery process of theexhaust gas purification device can be executed with reliability byincreasing the exhaust gas temperature irrespective of the operatingenvironment and the economic efficiency can be improved by keeping thefuel consumption at a minimum necessary level.

(2) In order to achieve the above second object, in an inventiondescribed in claim 2, the exhaust temperature increasing control devicein the exhaust gas purification system according to claim 1 controls anoperation amount of at least the latter one of the pump displacementadjusting device and the pump discharge pressure increasing device sothat an increment of the absorption torque of the hydraulic pump amountsto 20%-30% of maximum torque of the engine.

The present inventors have confirmed that the exhaust gas temperaturecan be increased to approximately 250° C.-350° C. without causing anyproblem to the operation of the hydraulic operating machine drivinghydraulic actuators if the hydraulic absorption torque generated by thepump displacement adjusting device and the pump discharge pressureincreasing device is approximately 20%-30% of the maximum torque of theengine. The present invention has been made based on these findings. Bycontrolling at least the operation amount of the pump discharge pressureincreasing device so that the increment of the absorption torque of thehydraulic pump amounts to 20%-30% of the maximum torque of the engine,unnecessary and excessive increase in the exhaust gas temperature can beavoided, the fuel consumption can be kept at a minimum necessary level,and the economic efficiency can be improved. Further, even in anoperating state (in which the operator is operating the machine), therecovery process of the exhaust gas purification device can be performedby increasing the exhaust gas temperature by the exhaust temperatureincreasing control without causing any problem to the operation of thehydraulic operating machine. Consequently, working efficiency can beincreased through the improvement of workability during the execution ofthe recovery control and the reduction of the operation interruptionfrequency of the hydraulic operating machine.

(3) In an invention described in claim 3, in the exhaust gaspurification system according to claim 1 or 2, the exhaust temperatureincreasing control device includes an exhaust temperature adjustingdevice which adjusts at least one selected from an operation amount ofthe pump displacement adjusting device, an operation amount of the pumpdischarge pressure increasing device and an increment of revolutionspeed of the engine so that the exhaust gas temperature remains within apreset range after the exhaust gas temperature detected by the exhausttemperature sensor has been increased to the preset value.

With this configuration, the exhaust gas temperature T can be reliablycontrolled and kept within the preset temperature range. Consequently,ill effect on the operation can be minimized in the recovery control inthe operating state. In the recovery control in the non-operating state,unnecessary increase in the engine load can be avoided, the fuelconsumption can be kept at a minimum necessary level, and the economicefficiency can be improved.

(4) In an invention described in claim 4, in the exhaust gaspurification system according to any one of claims 1-3, the recoverycontrol device is an automatic recovery control device whichautomatically starts operation when the exhaust resistance detected bythe exhaust resistance sensor has reached or exceeded the set value.

With this configuration, the recovery process of the exhaust gaspurification device can be executed with reliability by increasing theexhaust gas temperature even in low-load operation in the operatingstate.

(5) In an invention described in claim 5, the exhaust gas purificationsystem according to claim 4 further comprises operation detecting meansfor detecting whether the hydraulic actuator is being driven or not. Theexhaust temperature increasing control device increases the exhaust gastemperature by increasing the absorption torque of the hydraulic pump byoperating at least the latter one of the pump displacement adjustingdevice and the pump discharge pressure increasing device when thehydraulic actuator is being driven.

With this configuration, the recovery process of the exhaust gaspurification device can be executed with reliability by increasing theexhaust gas temperature even in low-load operation in the operatingstate.

(6) In an invention described in claim 6, in the exhaust gaspurification system according to claim 5, when the hydraulic actuator isnot being driven, the exhaust temperature increasing control deviceincreases the exhaust gas temperature by increasing revolution speed ofthe engine to a preset revolution speed and increasing the absorptiontorque of the hydraulic pump by operating the pump displacementadjusting device and the pump discharge pressure increasing device.

With this configuration, the recovery process of the exhaust gaspurification device can be executed with reliability even in thenon-operating state by securely increasing the exhaust gas temperatureby the combination of the absorption torque increasing control of thehydraulic pump and the engine revolution speed increasing control.

(7) In an invention described in claim 7, the exhaust gas purificationsystem according to any one of claims 1-3 further comprises: operationpermission state detecting means for detecting whether the hydraulicoperating machine is in an operation permission state or not; and manualrecovery instruction means. The recovery control device is a manualrecovery control device which issues an alarm when the exhaustresistance detected by the exhaust resistance sensor has reached orexceeded a second set value and starts operation when the operationpermission state detecting means detects that the hydraulic operatingmachine is not in the operation permission state and there is aninstruction by the manual recovery instruction means. The exhausttemperature increasing control device increases the exhaust gastemperature by increasing revolution speed of the engine to a presetrevolution speed and increasing the absorption torque of the hydraulicpump by operating the pump displacement adjusting device and the pumpdischarge pressure increasing device.

With this configuration, also in the manual recovery control, therecovery process of the exhaust gas purification device can be executedwith reliability by increasing the exhaust gas temperature irrespectiveof the operating environment and the economic efficiency can be improvedby keeping the fuel consumption at a minimum necessary level.

(8) In an invention described in claim 8, in the exhaust gaspurification system according to any one of claims 4-6, the exhausttemperature increasing control device previously stores an exhaustresistance threshold value, for judging whether the recovery of theexhaust gas purification device by the automatic recovery control deviceis necessary or not, as a function of engine revolution speed and anengine load, determines the exhaust resistance threshold value byreferring to current engine revolution speed and engine load andinputting them to the function, and sets the determined exhaustresistance threshold value as the set value.

With this configuration, an appropriate value incorporating theoperating status of the engine can be set as the set value, by whichproper recovery control can be performed.

(9) In an invention described in claim 9, in the exhaust gaspurification system according to claim 4, the automatic recovery controldevice sets the set value of the exhaust resistance at a lower valuewhen the hydraulic actuator is not being driven compared to cases wherethe hydraulic actuator is being driven.

With this configuration, in the non-operating state (when the hydraulicactuator is not being driven) in which the exhaust gas temperature isrelatively low and the particulate matter (PM) tends to accumulaterelatively more, the PM accumulated in the exhaust gas purificationdevice can be combusted more frequently than in the operating state(when the hydraulic actuator is being driven) and the exhaust gaspurification device can be recovered efficiently.

(10) In an invention described in claim 10, in the exhaust gaspurification system according to any one of claims 1-3, the recoverycontrol device includes an automatic recovery control device whichautomatically starts operation when the exhaust resistance detected bythe exhaust resistance sensor has reached or exceeded the set value anda manual recovery control device which issues an alarm when the exhaustresistance detected by the exhaust resistance sensor has reached orexceeded the set value and starts operation when the operationpermission state detecting means detects that the hydraulic operatingmachine is not in the operation permission state and there is aninstruction by the manual recovery instruction means. The set value inthe automatic recovery control device is set lower than the set value inthe manual recovery control device.

By setting the set value in the automatic recovery control device lowerthan the set value in the manual recovery control device as above, thefrequency of the automatic recovery control increases and the frequencyof the manual recovery control decreases due to the output value of theexhaust resistance sensor increasing to the second set value lessfrequently. Consequently, the operation interruption frequency of thehydraulic operating machine can be reduced.

Effect of the Invention

According to the present invention, the recovery process of the exhaustgas purification device can be executed with reliability by increasingthe exhaust gas temperature irrespective of the operating environmentand the economic efficiency can be improved by keeping the fuelconsumption at a minimum necessary level.

According to the present invention, the recovery process of the exhaustgas purification device can be executed with reliability by increasingthe exhaust gas temperature irrespective of the operating environment,the economic efficiency can be improved by keeping the fuel consumptionat a minimum necessary level, and the working efficiency can beincreased through the improvement of workability during the execution ofthe recovery control and the reduction of the operation interruptionfrequency of the hydraulic operating machine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a hydraulic driving system of ahydraulic operating machine equipped with an exhaust gas purificationsystem in accordance with a first embodiment of the present invention.

FIG. 2 is a flow chart showing the contents of a calculation process forpositive control and pump torque limiting control executed by acontroller.

FIG. 3 is a graph showing an absorption torque property of a hydraulicpump acquired as a result of pump torque limiting control.

FIG. 4 is a schematic diagram showing the external appearance of ahydraulic shovel as an example of the hydraulic operating machineequipped with the hydraulic driving system and the exhaust gaspurification system shown in FIG. 1.

FIG. 5 is a flow chart showing the overall process flow of automaticrecovery control when the hydraulic operating machine is in an operationpermission state.

FIG. 6 is a flow chart showing the contents of the automatic recoverycontrol when the hydraulic operating machine is in the operationpermission state and in an operating state.

FIG. 7 is a flow chart showing the contents of the automatic recoverycontrol when the hydraulic operating machine is in the operationpermission state and in a non-operating state.

FIG. 8 is a flow chart showing the contents of manual recovery controlwhen the hydraulic operating machine is in an operation prohibitionstate.

FIG. 9 is a graph showing the relationship between the amount of PMaccumulated on a filter in an exhaust gas purification device and theexhaust resistance of the filter (differential pressure across thefilter) at the rated engine revolution speed and the maximum engineload.

FIG. 10 is a graph showing changes in the relationship between the PMaccumulation amount and the exhaust resistance shown in FIG. 9 dependingon the engine revolution speed and the engine load.

FIG. 11 is a flow chart showing the contents of exhaust gas temperatureincreasing control (step S312 in FIG. 6).

FIG. 12 is a flow chart showing the contents of a process includingexhaust gas temperature increasing control (step S412 in FIG. 7).

FIG. 13 is a schematic diagram showing a hydraulic driving system of ahydraulic operating machine equipped with an exhaust gas purificationsystem in accordance with a second embodiment of the present invention.

FIG. 14 is a flow chart showing the contents of a calculation processfor the positive control of the hydraulic pump executed by a controller.

FIG. 15 is a graph like FIG. 3 showing the absorption torque property ofthe hydraulic pump acquired as a result of the pump torque limitingcontrol.

FIG. 16 is a flow chart showing the details of the hydraulic absorptiontorque increasing control in the step S312 in FIG. 6 regarding theautomatic recovery control in the operating state.

FIG. 17 is a flow chart (corresponding to FIG. 6 in the firstembodiment) showing the contents of the automatic recovery control inthe operating state executed by an exhaust gas purification system inaccordance with a third embodiment of the present invention.

FIG. 18 is a flow chart (corresponding to FIG. 7 in the firstembodiment) showing the contents of the automatic recovery control inthe non-operating state executed by the exhaust gas purification systemof the third embodiment of the present invention.

FIG. 19 is a flow chart (corresponding to FIG. 8 in the firstembodiment) showing the contents of the manual recovery control executedby the exhaust gas purification system of the third embodiment of thepresent invention when the hydraulic operating machine is in theoperation prohibition state.

MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings, a description will be given in detail ofpreferred embodiments in accordance with the present invention.

FIG. 1 is a schematic diagram showing a hydraulic driving system of ahydraulic operating machine equipped with an exhaust gas purificationsystem in accordance with a first embodiment of the present invention.

In FIG. 1, the hydraulic driving system comprises a diesel engine(hereinafter properly abbreviated as an “engine”) 1, a main hydraulicpump 2 of the variable displacement type, a pilot pump 3, a hydraulicactuator 25, flow/directional control valves 4 and 5, a control leverdevice 8 and a main relief valve 9. The hydraulic pump 2 and the pilotpump 3 are driven by the engine 1. The hydraulic actuator 25 is drivenby hydraulic fluid (oil) discharged from the hydraulic pump 2. Theflow/directional control valve 4 controls the flow rate and thedirection of the hydraulic fluid supplied from the hydraulic pump 2 tothe hydraulic actuator 25. The flow/directional control valve 5 controlsthe flow rate and the direction of hydraulic fluid supplied from thehydraulic pump 2 to other hydraulic actuators (not shown). The controllever device 8 is used for operating the hydraulic actuator 25. The mainrelief valve 9 regulates the maximum pressure of a discharging hydraulicline of the hydraulic pump 2.

The control lever device 8 includes pilot valves (pressure reducingvalves) 8 a and 8 b, to which hydraulic fluid is supplied from the pilotpump 3. The discharge pressure of the pilot pump 3 is controlled by apilot relief valve 10 at a constant level. When a control lever 8 c ofthe control lever device 8 is operated, either the pilot valve 8 a orthe pilot valve 8 b moves depending on the direction and the amount ofthe operation, by which operating pilot pressure is generated. By theoperating pilot pressure, a spool of the flow/directional control valve4 is slid and the hydraulic actuator 25 is operated.

The hydraulic driving system further comprises a pilot cut valve 11, asafety lever 12, a switch 13, a regulator 14, pressure sensors 16 and17, a revolution sensor 18, an engine control dial 19 and a controller20. The pilot cut valve 11 is attached to a discharging hydraulic lineof the pilot pump 3. The safety lever 12 (called “gate lock lever”) isplaced at the entrance to the operator's seat. The switch 13 (operationpermission state detecting means) operates in conjunction with thesafety lever 12. The regulator 14 (pump displacement adjusting device)adjusts the tilting angle (capacity or displacement volume) of thehydraulic pump 2. The pressure sensor 16 (operation detecting means)detects the operating pilot pressure generated by the pilot valves 8 aand 8 b as the operation amount of the control lever device 8. Thepressure sensor 17 detects the discharge pressure of the hydraulic pump2. The revolution sensor 18 detects the revolution speed of the engine1. The engine control dial 19 outputs an instruction signal whichspecifies a target revolution speed of the engine 1.

A plurality of shuttle valves (including shuttle valves 21 a and 21 b)are arranged along signal paths for the pressure sensor 16 for detectingthe operating pilot pressure. When the operating pilot pressure isgenerated by either the pilot valve 8 a or 8 b, the operating pilotpressure is lead to the pressure sensor 16 via the shuttle valves 21 aand 21 b and is detected by the pressure sensor 16. Also when a controllever device for another actuator (not shown) is operated and operatingpilot pressure is generated accordingly, the operating pilot pressure islead to the pressure sensor 16 via a shuttle valve (not shown) and theshuttle valve 21 b and is detected by the pressure sensor 16.

When the hydraulic actuator 25 is operated, the controller 20 detectsthe operation amount of the control lever device 8 and the enginerevolution speed at that time with the pressure sensor 16 and therevolution sensor 18, respectively, calculates a target tilting angle ofthe hydraulic pump 2 through a calculation process for positive controland pump torque limiting control (also called “pump horsepowercontrol”), and changes the tilting angle of the hydraulic pump 2 bycontrolling the regulator 14 to achieve the target tilting angle.

The safety lever 12 can be operated to an operation permission positionand an operation prohibition position. The switch 13 remains in an ONstate when the safety lever 12 is at the operation permission position,and in an OFF state when the safety lever 12 is at the operationprohibition position. The controller 20 detects the ON/OFF state of theswitch 13 operating in conjunction with the safety lever 12 as above andopens the pilot cut valve 11 to supply the hydraulic fluid to the pilotvalves 8 a and 8 b of the control lever device 8 only when the safetylever 12 is at the operation permission position (only when the switch13 is ON).

Further, the instruction signal from the engine control dial 19 isinputted to the controller 20. The controller 20 controls the revolutionspeed and torque of the engine 1 by controlling an electronic governor 1a (which controls the fuel injection quantity of the engine 1) accordingto the instruction signal and the measurement value of the revolutionsensor 18 (current engine revolution speed).

The contents of the calculation process for the positive control and thepump torque limiting control of the hydraulic pump 2 executed by thecontroller 20 will be explained below referring to FIG. 2. FIG. 2 is aflow chart showing the contents of the calculation process for thepositive control and the pump torque limiting control executed by thecontroller 20.

First, the controller 20 calculates a demanded flow rate Qr for thepositive control by detecting the operation amount of the control leverdevice 8 with the pressure sensor 16 (step S10). This calculation isexecuted by multiplying the measurement value of the pressure sensor 16by a prescribed demanded flow rate conversion factor, for example.Subsequently, the controller 20 calculates the target tilting angle qrof the hydraulic pump 2 necessary for making the hydraulic pump 2discharge the demanded flow rate Qr (step S15). This calculation isexecuted by dividing the demanded flow rate Qr by the revolution speedof the hydraulic pump 2 and multiplying the quotient by a prescribedconversion factor. The revolution speed of the hydraulic pump 2 isdetermined from the measurement value of the revolution sensor 18.Subsequently, the controller 20 calculates a maximum tilting angle qmaxof the hydraulic pump 2 for the pump torque limiting control accordingto the discharge pressure Pp of the hydraulic pump 2 inputted from thepressure sensor 17 (step S20). This calculation is executed bypreviously setting a constant maximum absorption torque property of thehydraulic pump 2, checking the discharge pressure Pp of the hydraulicpump 2 with the property, and thereby determining a correspondingtilting angle (maximum tilting angle). Subsequently, the controller 20compares the target tilting angle qr with the maximum tilting angle qmax(step S25). When the target tilting angle qr is less than the maximumtilting angle qmax, the controller 20 calculates a control signal forachieving the target tilting angle qr and outputs the control signal tothe regulator 14 (step S30). In contrast, when the target tilting angleqr is the maximum tilting angle qmax or greater, the controller 20calculates a control signal for achieving the maximum tilting angle qmaxand outputs the control signal to the regulator 14 (step S35). With thecontrol signal, when the target tilting angle qr of the hydraulic pump 2is less than the maximum tilting angle qmax, the regulator 14 changesthe tilting angle of the hydraulic pump 2 so as to achieve the targettilting angle qr (positive control). When the target tilting angle qr ofthe hydraulic pump 2 is the maximum tilting angle qmax or greater, theregulator 14 changes the tilting angle of the hydraulic pump 2 so as tolimit the tilting angle to the maximum tilting angle qmax (pump torquelimiting control or pump horsepower control).

FIG. 3 is a graph showing an absorption torque property of the hydraulicpump 2 acquired as a result of the pump torque limiting control, whereinthe horizontal axis represents the discharge pressure Pp of thehydraulic pump 2 and the vertical axis represents the tilting angle(displacement) q of the hydraulic pump 2.

In FIG. 3, the absorption torque property of the hydraulic pump 2 ismade up of a constant maximum tilting angle property line Tp0 and aconstant maximum absorption torque property line Tp1.

When the discharge pressure Pp of the hydraulic pump 2 is not higherthan a first value P0 defined as the pressure at the turning point(transition point) from the constant maximum tilting angle property lineTp0 to the constant maximum absorption torque property line Tp1, themaximum tilting angle (maximum displacement) qmax of the hydraulic pump2 remains at a constant value q0 (which is determined by the mechanismof the hydraulic pump 2) even with the increase in the dischargepressure Pp of the hydraulic pump 2. In this case, the maximumabsorption torque of the hydraulic pump 2 (product of the pump dischargepressure and the pump tilting angle) increases with the increase in thedischarge pressure Pp of the hydraulic pump 2. As the discharge pressurePp of the hydraulic pump 2 increases over the first value P0, themaximum tilting angle qmax of the hydraulic pump 2 decreases along theconstant maximum absorption torque property line Tp1 and the absorptiontorque of the hydraulic pump 2 is kept at maximum torque Tmax which isdetermined by the property line Tp1. This is a control partcorresponding to the aforementioned steps S25 and S35. Here, theproperty line Tp1 is a part of a hyperbolic curve and the maximum torqueTmax determined by the property line Tp1 has been set slightly lowerthan limit torque TEL of the engine 1. With this setting, when thedischarge pressure Pp of the hydraulic pump 2 increases over the firstvalue P0, the absorption torque (input torque) of the hydraulic pump 2is controlled so as not to exceed the preset maximum torque Tmax (so asnot to exceed the limit torque TEL of the engine 1) by decreasing themaximum tilting angle qmax of the hydraulic pump 2.

The exhaust gas purification system in accordance with this embodimentis installed in such a hydraulic driving system. The exhaust gaspurification system comprises an exhaust gas purification device 32placed in an exhaust line 31 constituting the exhaust system of theengine 1, an exhaust temperature sensor 33 placed at the inlet of theexhaust gas purification device 32 for detecting the temperature of theexhaust gas inside the exhaust gas purification device, an exhaustresistance sensor 34 for detecting exhaust resistance of a filter insidethe exhaust gas purification device 32, a manual recovery switch 36 usedfor instructing the exhaust gas purification system (controller 20) tostart manual recovery control, and an alarm lamp 37 for informing theoperator that the a manual recovery process is necessary. Output valuesof the sensors/switch are inputted to the controller 20. The exhaust gaspurification system further comprises a solenoid proportional valve 38(pump discharge pressure increasing device) provided in the discharginghydraulic line 2 a of the hydraulic pump 2. The solenoid proportionalvalve 38 is a variable throttle valve which changes its opening areaaccording to instruction current supplied to its solenoid. The solenoidproportional valve 38 stays at the full open position shown in thefigure when the instruction current is minimum (OFF), decreases theopening area with the increase in the instruction current, and minimizesthe opening area (totally closed state) when the instruction current ismaximum.

The exhaust gas purification device 32 includes the filter, with whichparticulate matter (PM) contained in the exhaust gas is collected. Theexhaust gas purification device 32 is also equipped with an oxidationcatalyst. When the exhaust gas temperature exceeds a prescribedtemperature, the oxidation catalyst is activated and causes combustionof unburned fuel added to the exhaust gas, an increase in the exhaustgas temperature, and combustion of the collected PM accumulated on thefilter.

Specifically, the exhaust gas purification device 32 is equipped with afilter with an oxidation catalyst and another oxidation catalyst placedupstream of the filter, for example. In this case, the prescribedtemperature (recovery start temperature) for the activation of theoxidation catalyst is approximately 250° C., for example. When theexhaust gas temperature exceeds approximately 250° C., the oxidationcatalyst is activated and the collected PM accumulated on the filter iscombusted. The exhaust gas purification device 32 may also beimplemented by the filter with the oxidation catalyst only. In thiscase, the prescribed temperature (recovery start temperature) for theactivation of the oxidation catalyst is approximately 350° C., forexample.

The exhaust resistance sensor 34 is a differential pressure detectingdevice for detecting the differential pressure between the upstream sideand the downstream side of the filter of the exhaust gas purificationdevice 32 (pressure loss of the filter), for example.

FIG. 4 is a schematic diagram showing the external appearance of ahydraulic shovel as an example of the hydraulic operating machineequipped with the hydraulic driving system and the exhaust gaspurification system shown in FIG. 1.

The hydraulic shovel comprises a lower travel structure 100, an upperswing structure 101 and a front work implement 102. The lower travelstructure 100 is equipped with right and left crawler travel devices 103a and 103 b, which are driven by right and left travel motors 104 a and104 b, respectively. The upper swing structure 101 is mounted on thelower travel structure 100 so that it can be swiveled by a swing motor105. The front work implement 102 is attached to the front part of theupper swing structure 101 so that it can be elevated and lowered. Theupper swing structure 101 includes an engine room 106 and a cab 107. Theengine 1 is installed in the engine room 106. The safety lever (gatelock lever) 12 is placed in the cab 107 at a position close to theentrance to the operator's seat. The control lever devices are arrangedto the right and left of the operator's seat.

The front work implement 102 is an articulated structure including aboom 111, an arm 112 and a bucket 113. The boom 111 is rotated and movedin the vertical direction by the expansion and contraction of a boomcylinder 114. The arm 112 is rotated and moved in the vertical directionand the front-to-back direction by the expansion and contraction of anarm cylinder 115. The bucket 113 is rotated and moved in the verticaldirection and the front-to-back direction by the expansion andcontraction of a bucket cylinder 116.

In FIG. 1, the hydraulic actuator 25 corresponds to the swing motor 105,for example, and the control lever device 8 corresponds to one of thecontrol lever devices arranged to the right and left of the operator'sseat. Other hydraulic actuators and control valves (the travel motors104 a and 104 b, the boom cylinder 114, the arm cylinder 115, the bucketcylinder 116, etc.) are not shown in FIG. 1.

Next, the operation of the exhaust gas purification system of thisembodiment will be described below while explaining a process executedby the controller 20 with reference to FIGS. 5-8.

FIGS. 5-8 are flow charts showing the contents of a filter recoverycalculation process executed by the controller 20. FIG. 5 shows theoverall process flow of automatic recovery control when the hydraulicoperating machine (hereinafter referred to simply as a “machine”) is inan operation permission state. FIG. 6 shows the contents of theautomatic recovery control when the machine is in the operationpermission state and in an operating state (i.e., when the operator isoperating the machine). FIG. 7 shows the contents of the automaticrecovery control when the machine is in the operation permission stateand in a non-operating state (i.e., when the operator is not operatingthe machine). FIG. 8 shows the contents of the manual recovery controlwhen the machine is in an operation prohibition state. Each of theprocesses of FIGS. 5-8 is executed repeatedly at preset periods (controlcycles).

First, the overall process flow of the automatic recovery control whenthe machine is in the operation permission state will be explainedreferring to FIG. 5.

The controller 20 first judges whether the safety lever 12 is at theoperation permission position or not by detecting whether the switch 13operating in conjunction with the safety lever 12 is in the ON state ornot (step S100). When the switch 13 is in the OFF state, that is, whenthe safety lever 12 is not at the operation permission position (i.e.,at the operation prohibition position), the machine is in the operationprohibition state. In this case, the process in the current controlcycle is ended without any further processing. When the switch 13 is inthe ON state, that is, when the safety lever 12 is at the operationpermission position, the machine is in the operation permission state.In this case, the process advances to the next step.

In the next step, the controller 20 judges whether any one of thecontrol lever devices is being operated by the operator or not bydetecting the output pressures of all the control lever devices(including the control lever device 8) based on the output values of thepressure sensor 16 and checking whether each of the output pressures isat a level indicating the operator's operation to a correspondingcontrol lever device or not (step S200). When any one of the controllever devices is being operated by the operator, the machine is beingoperated (operating state). In this case, the controller 20 executesautomatic recovery control in the operating state (step S300). When noneof the control lever devices is being operated by the operator, themachine is not being operated (non-operating state). In this case, thecontroller 20 executes automatic recovery control in the non-operatingstate (step S400).

The details of the automatic recovery control in the operating statewill be explained referring to FIG. 6.

First, the controller 20 calculates an exhaust resistance thresholdvalue ΔPa for judging whether the automatic recovery control isnecessary or not and sets the calculated exhaust resistance thresholdvalue ΔPa as a first set value (step S305).

Here, the exhaust resistance threshold value ΔPa for judging whether theautomatic recovery control is necessary or not will be explainedreferring to FIGS. 9 and 10.

FIG. 9 is a graph showing the relationship between the amount of PMaccumulated on the filter in the exhaust gas purification device 32 andthe exhaust resistance of the filter (differential pressure across thefilter) at the rated engine revolution speed and the maximum engineload. FIG. 10 is a graph showing changes in the relationship between thePM accumulation amount and the exhaust resistance depending on theengine revolution speed and the engine load.

Referring to FIG. 9, the differential pressure across the filterincreases with the increase in the PM accumulation amount of the filter.In FIG. 9, “ΔPLIMIT” represents the exhaust resistance at a limitaccumulation amount WLIMIT of the PM (limit exhaust resistance). Thelimit accumulation amount WLIMIT means an accumulation amount at whichfurther PM accumulation on the filter can cause abnormal combustion.“ΔPb” represents an exhaust resistance threshold value (second setvalue) at a PM accumulation amount Wb for judging whether the manualrecovery control is necessary or not. This threshold value is set asclose to the PM exhaust resistance ΔPLIMIT as possible. “ΔPc” representsan exhaust resistance threshold value at a PM accumulation amount We forjudging whether the recovery control should be ended or not. An exhaustresistance threshold value ΔPa at a PM accumulation amount Wa, forjudging whether the automatic recovery control is necessary or not, hasbeen set at a value lower than the threshold value (second set value)ΔPb for the manual recovery control. For example, the threshold valueΔPa has been set at approximately 40%-60% of the threshold value ΔPb(ΔPa<ΔPb).

The relationship between the PM accumulation amount and the exhaustresistance shown in FIG. 9 is that at the rated engine revolution speedand the maximum engine load. The relationship changes depending on theengine revolution speed and the engine load as shown in FIG. 10.Specifically, even if the PM accumulation amount of the filter remainsconstant, an increase in the engine revolution speed or the engine loadcauses an increase in the exhaust resistance of the filter since thefuel injection quantity of the electronic governor 1 a increasescorrespondingly and the flow rate of the exhaust gas increases.Inversely, a decrease in the engine revolution speed or the engine loadcauses a decrease in the exhaust resistance of the filter since the fuelinjection quantity of the electronic governor 1 a decreasescorrespondingly and the flow rate of the exhaust gas decreases.Consequently, the relationship between the PM accumulation amount andthe exhaust resistance changes as shown in FIG. 10 in response to theincrease/decrease in the engine revolution speed or the engine load.

The controller 20 previously stores the exhaust resistance thresholdvalue ΔPa (for judging whether the automatic recovery control isnecessary or not) as a function of the engine revolution speed and theengine load based on the relationships between the PM accumulationamount and the exhaust resistance like those shown in FIG. 10. In thestep S305, the controller 20 determines the exhaust resistance thresholdvalue ΔPa by referring to the current engine revolution speed and thecurrent engine load and inputting them to the function. The measurementvalue of the revolution sensor can be used as the current enginerevolution speed, and a target fuel injection quantity (as an internalvalue of the electronic governor 1 a) can be used as the current engineload. It is also possible to calculate the absorption torque of thehydraulic pump 2 from the tilting angle and the discharge pressure ofthe hydraulic pump 2 and use the calculated absorption torque as theengine load.

By determining the exhaust resistance threshold value ΔPa (for judgingwhether the automatic recovery control is necessary or not) bycalculation and setting the threshold value ΔPa as the first set valueas explained above, an appropriate threshold value ΔPa incorporating theoperating status of the engine can be set and the recovery control canbe started properly.

In the next step, the controller 20 detects the exhaust resistance ΔP ofthe filter in the exhaust gas purification device 32 based on the outputvalue of the exhaust resistance sensor 34 and then judges whether or notthe exhaust resistance ΔP is the first set value ΔPa or higher (stepS310). When the exhaust resistance ΔP is less than the first set valueΔPa, the controller 20 ends the process in the current control cyclewithout any further processing since the PM accumulation has notproceeded to the point at which the filter of the exhaust gaspurification device 32 needs the recovery by the automatic recoverycontrol. When the exhaust resistance ΔP is the first set value ΔPa orhigher, the process advances to the next step.

In the next step, the controller 20 starts the automatic recoverycontrol.

At the start of the automatic recovery control, exhaust gas temperatureincreasing control is executed (step S312). In the exhaust gastemperature increasing control, hydraulic absorption torque increasingcontrol is carried out. Specifically, the discharge pressure of thehydraulic pump 2 is increased by operating the solenoid proportionalvalve 38 and reducing its opening area. Further, the discharge flow rateof the hydraulic pump 2 is raised by increasing the tilting angle(displacement) of the hydraulic pump 2. By increasing the dischargepressure and the tilting angle (displacement) of the hydraulic pump 2,the absorption torque of the hydraulic pump 2 (hydraulic absorptiontorque) is increased and the engine load is increased. The increment ofthe absorption torque of the hydraulic pump 2 in this case is 20%-30%(preferably, about 30%) of the maximum torque of the engine 1. With thissetting, the engine 1 injects a correspondingly larger amount of fuel,by which the exhaust gas temperature can be increased.

The details of the hydraulic absorption torque increasing control (stepS312) will be explained referring to FIG. 11. FIG. 11 is a flow chartshowing the contents of the hydraulic absorption torque increasingcontrol.

First, the controller 20 acquires the target tilting angle qr of thehydraulic pump 2 calculated in the step S15 in FIG. 2 (step S50). Atarget tilting angle qco and a target pressure Pco for the hydraulicabsorption torque increasing control have previously been set to thecontroller 20. The controller 20 compares the target tilting angle qrfor the positive control with the target tilting angle qco for thehydraulic absorption torque increasing control (step S55). When thetarget tilting angle qr for the positive control is less than or equalto the target tilting angle qco for the hydraulic absorption torqueincreasing control, the controller 20 invalidates the calculationprocess for the positive control and the pump torque limiting control inthe flow chart of FIG. 2 (step S60). Subsequently, the controller 20calculates a control signal for achieving the target tilting angle qcofor the hydraulic absorption torque increasing control and a controlsignal for achieving the target pressure Pco for the hydraulicabsorption torque increasing control, outputs the former control signalto the regulator 14, and outputs the latter control signal to thesolenoid proportional valve 38 (step S65). In contrast, when the targettilting angle qr for the positive control is greater than the targettilting angle qco for the hydraulic absorption torque increasingcontrol, the controller 20 validates the calculation process for thepositive control and the pump torque limiting control in the flow chartof FIG. 2 (step S70). Subsequently, the controller 20 calculates acontrol signal for achieving the target pressure Pco for the hydraulicabsorption torque increasing control and outputs the control signal tothe solenoid proportional valve 38 (step S75).

In FIG. 3, the point A is the operating point of the hydraulic pump 2when the hydraulic absorption torque increasing control is not executedin the non-operating state. In the non-operating state in which nocontrol lever device is being operated, the demanded flow rate for thepositive control equals 0 and the hydraulic pump 2 is held at a minimumtilting angle qmin (point A). Further, in the non-operating state inwhich no control lever device is being operated, every flow/directionalcontrol valve 4, 5 is at the center valve position shown in the figureand the hydraulic pump 2 remains at a minimum discharge pressure Ppmin(point A). In FIG. 3, the point B is the operating point of thehydraulic pump 2 when the hydraulic absorption torque increasing controlis executed in the non-operating state (explained later). Either in thenon-operating state or in the operating state, the target tilting anglefor the hydraulic absorption torque increasing control is set at qco andthe target pressure is set at Pco. Thus, in the steps S65 and S75 inFIG. 11, the hydraulic absorption torque increasing control is carriedout using the target tilting angle qco and the target pressure Pco atthe point B.

In this case, the controller 20 controls the operation amounts of theregulator 14 and the solenoid proportional valve 38 by setting thetarget tilting angle qco and the target pressure Pco so that theincrement of the absorption torque of the hydraulic pump 2 by thehydraulic absorption torque increasing control amounts to 20%-30%(preferably, about 30%) of the maximum torque of the engine 1. In anexamination conducted by the present inventors, it has been confirmedthat even in low-load operation, the exhaust gas temperature can beraised to approximately 250° C. when the hydraulic absorption torque isincreased by approximately 20% of the maximum engine torque, and toapproximately 350° C. when the hydraulic absorption torque is increasedby approximately 30% of the maximum engine torque. We have alsoconfirmed that no problem in terms of operation occurs even if themachine is operated in the state in which the hydraulic absorptiontorque has been created by the solenoid proportional valve 38 as long asthe increment is approximately 30% of the maximum engine torque.

Subsequently, the controller 20 judges whether or not the temperature Tof the exhaust gas inside the exhaust gas purification device 32 is apreset threshold value Ta or higher based on the output value of theexhaust temperature sensor 33 (step S315). The judgment is repeatedunless the exhaust gas temperature T is judged to be the threshold valueTa or higher. When the exhaust gas temperature T is judged to be thethreshold value Ta or higher, the controller 20 starts the recoverycontrol (step S320). The threshold value Ta may be set at, for example,approximately 250° C. (activation temperature of the oxidation catalyst)in the case where the oxidation catalyst is placed upstream of thefilter in the exhaust gas purification device 32. In the case where onlythe filter with an oxidation catalyst is arranged in the exhaust gaspurification device 32, the threshold value Ta may be set atapproximately 350° C. (activation temperature of the oxidationcatalyst), for example.

In the recovery control in the step S320, post-injection (additionalinjection) in the expansion stroke after the main injection of theengine is carried out by controlling the electronic governor 1 a of theengine 1. By the post-injection, unburned fuel is introduced into theexhaust gas. The unburned fuel is combusted by the activated oxidationcatalyst, by which the exhaust gas temperature is raised and the PMaccumulated on the filter is combusted and removed by thehigh-temperature exhaust gas.

Subsequently, the controller 20 calculates and sets the exhaustresistance threshold value ΔPc for judging whether the recovery controlshould be ended or not (step S340). The idea for the calculation of thethreshold value ΔPc is similar to that for the calculation of thethreshold value ΔPa. Specifically, the controller 20 previously storesthe exhaust resistance threshold value ΔPc (for judging whether theautomatic recovery control should be ended or not) as a function of theengine revolution speed and the engine load based on the relationshipsbetween the PM accumulation amount and the exhaust resistance like thoseshown in FIG. 10. In the step S340, the controller 20 determines theexhaust resistance threshold value ΔPc by referring to the currentengine revolution speed and the current engine load and inputting themto the function. By the above calculation and setting, an appropriatethreshold value ΔPc incorporating the operating status of the engine canbe set and the recovery control can be ended properly.

The exhaust gas temperature increasing control (hydraulic absorptiontorque increasing control) and the recovery control (additional fuelinjection) are executed until the exhaust resistance ΔP of the exhaustgas purification device 32 falls below the threshold value ΔPc. When theexhaust resistance ΔP of the exhaust gas purification device 32 isjudged to be below the threshold value ΔPc, the controller 20 ends theautomatic recovery control, puts the solenoid proportional valve 38 inthe full open state by stopping activating the valve, and thereby endsthe exhaust gas temperature increasing control (hydraulic absorptiontorque increasing control) and the recovery control (additional fuelinjection) (steps S320, S340, S345 and S350).

Next, the details of the automatic recovery control in the non-operatingstate will be explained referring to FIG. 7.

A hydraulic operating machine (hydraulic shovel) is generally equippedwith an automatic idling function. The automatic idling function is atechnique for reducing the engine revolution speed to an idlingrevolution speed a prescribed time period (e.g., 5 seconds) after thecontrol lever 8 c of the control lever device 8 is returned from itsoperating position to its neutral position. Thus, in the non-operatingstate, the engine 1 is mostly in the idling revolution state. Therefore,in the automatic recovery control in the non-operating state, thehydraulic absorption torque increasing control and an engine revolutionspeed increasing control are executed in the exhaust gas temperatureincreasing control (step S412). The increment of the absorption torqueof the hydraulic pump 2 in the hydraulic absorption torque increasingcontrol is 20%-30% (preferably, about 30%) of the maximum torque of theengine 1 similarly to the case in the operating state. In the enginerevolution speed increasing control, the engine revolution speed isincreased to approximately 1700 rpm, for example.

FIG. 12 is a flow chart showing the contents of a process including thehydraulic absorption torque increasing control and the engine revolutionspeed increasing control executed in the step S412 in FIG. 7.

The controller 20 calculates the aforementioned control signal forachieving the target tilting angle qco for the hydraulic absorptiontorque increasing control and the aforementioned control signal forachieving the target pressure Pco for the hydraulic absorption torqueincreasing control, outputs the former control signal to the regulator14, and outputs the latter control signal to the solenoid proportionalvalve 38 (step S80). According to the control signals, the hydraulicpump 2 operates at the operating point B shown in FIG. 3. The controller20 also executes the engine revolution speed increasing control so as toincrease the engine revolution speed to approximately 1700 rpm (stepS85).

Returning to FIG. 7, steps S405, S410, S415, S420, S440, S445 and S450are executed in the same way as the steps S305, S310, S315, S320, S340,S345 and S350 in FIG. 6.

Incidentally, the exhaust resistance threshold value (first set value)used for starting the automatic recovery control in the non-operatingstate may be set lower than the threshold value ΔPa which is used forstarting the automatic recovery control in the operating state. In thesteps S405 and S410 in FIG. 7, the threshold value set lower than ΔPa isexpressed as “ΔPd” in parentheses (ΔPd<ΔPa). The threshold value ΔPd isindicated in FIG. 9 as the exhaust resistance at a PM accumulationamount Wd. By use of the threshold value ΔPd, in the non-operating statein which the exhaust gas temperature is relatively low and the PM tendsto accumulate relatively more, the PM accumulated on the filter can becombusted more frequently than in the operating state and the filter canbe recovered efficiently.

Further, the increment of the absorption torque of the hydraulic pump 2(hydraulic absorption torque) in the hydraulic absorption torqueincreasing control in the step S412 may be set greater than 30% of themaximum engine torque (the increment in the operating state) since noproblem occurs even if the absorption torque of the hydraulic pump 2 isincreased greatly in the non-operating state. With such a setting, thespeed of the exhaust gas temperature increasing control in thenon-operating state can be increased and the filter recovery process canbe performed quickly.

Next, the manual recovery control which is executed when the machine isin the operation prohibition state will be explained referring to FIG.8.

First, the controller 20 detects the exhaust resistance ΔP of theexhaust gas purification device 32 based on the output value of theexhaust resistance sensor 34 and then judges whether or not the exhaustresistance ΔP is the second set value ΔPb (previously set as the exhaustresistance threshold value for judging whether the manual recoverycontrol is necessary or not) or higher (step S500). Since the enginerevolution speed and the engine load are controlled at substantiallyconstant levels in the manual recovery control (as will be explainedlater), the exhaust resistance threshold value for judging whether themanual recovery control is necessary or not may be previously determinedand set as a fixed value as an exhaust resistance value corresponding tothe constant engine revolution speed and the constant engine load. Thesame goes for the exhaust resistance threshold value ΔPc (for judgingwhether the recovery control should be ended or not) which will beexplained later.

As explained referring to FIG. 9, the second set value ΔPb has been setto satisfy the relationship ΔPa<ΔPb with the first set value ΔPa and tobe as close to the exhaust resistance ΔPLIMIT at the limit PMaccumulation amount WLIMIT as possible.

When the exhaust resistance ΔP is less than the second set value ΔPb,the controller 20 ends the process in the current control cycle withoutany further processing since the PM accumulation has not proceeded tothe point at which the filter of the exhaust gas purification device 32needs the recovery by the manual recovery control. When the exhaustresistance ΔP is the second set value ΔPb or higher, the processadvances to the next step.

In the next step, the controller 20 lights up the alarm lamp 37 andthereby informs the operator that the manual recovery process isnecessary (step S510).

Subsequently, the controller 20 judges whether the safety lever 12 is atthe operation prohibition position or not by detecting whether theswitch 13 operating in conjunction with the safety lever 12 is in theOFF state or not (step S520). When the switch 13 is in the ON state,that is, when the safety lever 12 is not at the operation prohibitionposition (i.e., at the operation permission position), the machine is inthe operation permission state. In this case, the machine is in a stateunsuitable for the manual recovery control, and thus the controller 20ends the process in the current control cycle without any furtherprocessing. When the switch 13 is in the OFF state, that is, when thesafety lever 12 is at the operation prohibition position, the machine isin the operation prohibition state. In this case, the process advancesto the next step.

In the next step, the controller 20 judges whether the manual recoveryswitch 36 has been turned ON or not (step S530). When the manualrecovery switch 36 has not been turned ON, the controller 20 ends theprocess in the current control cycle without any further processing.When the manual recovery switch 36 has been turned ON, the processadvances to the next step.

In the next step, the controller 20 extinguishes the alarm lamp 37 (stepS540) and executes the exhaust gas temperature increasing control byperforming the hydraulic absorption torque increasing control and theengine revolution speed increasing control (step S545) similarly to theautomatic recovery control shown in FIG. 7.

Specifically, in the case of the manual recovery control, the engine 1is necessarily in the idling revolution state since the safety lever isat the operation prohibition position, the pilot cut valve 11 has beenclosed and the machine is in an inoperable state (in which operation tothe machine is impossible). Therefore, in the step S545, the increase inthe exhaust gas temperature is promoted by executing the hydraulicabsorption torque increasing control (20%-30% (preferably, about 30%) ofthe maximum torque of the engine 1) and the engine revolution speedincreasing control (approximately 1700 rpm, for example) similarly tothe step S412 in the automatic recovery control in the non-operatingstate shown in FIG. 7.

Also when the machine is in the inoperable state (in which operation tothe machine is impossible), no problem occurs even if the absorptiontorque of the hydraulic pump 2 is increased greatly. Therefore,similarly to the step S412 in the automatic recovery control in thenon-operating state shown in FIG. 7, the increment of the absorptiontorque of the hydraulic pump 2 (hydraulic absorption torque) in thehydraulic absorption torque increasing control in the step S545 may beset greater than 30% of the maximum engine torque (the increment in theoperating state). With such a setting, the speed of the exhaust gastemperature increasing control in cases where the machine is in theinoperable state can be increased and efficient recovery control of thefilter becomes possible.

In the above explanation, the solenoid proportional valve 38 forms apump discharge pressure increasing device which is provided in thehydraulic line 2 a (through which the hydraulic fluid discharged fromthe hydraulic pump 2 flows) and increases the discharge pressure of thehydraulic pump 2. The processing function of the controller 20 in thesteps S305-S350 in FIG. 6, the steps S405-S450 in FIG. 7 and the stepsS500-S610 in FIG. 8 forms a recovery control device which executes therecovery of the exhaust gas purification device 32 by combusting andremoving the particulate matter accumulated in the exhaust gaspurification device 32 when the exhaust resistance detected by theexhaust resistance sensor 34 has reached or exceeded the set value ΔPaor ΔPb.

The processing function of the controller 20 in the steps S312 and S315in FIG. 6, the steps S412 and S415 in FIG. 7 and the steps S545 and S550in FIG. 8 forms an exhaust temperature increasing control device whichincreases the exhaust gas temperature so as to make the exhaust gastemperature detected by the exhaust temperature sensor 33 reach a presetvalue by increasing the absorption torque of the hydraulic pump 2 byoperating at least the latter one (solenoid proportional valve 38) ofthe regulator 14 (pump displacement adjusting device) and the solenoidproportional valve 38 (pump discharge pressure increasing device) whenthe exhaust resistance detected by the exhaust resistance sensor 34 hasreached or exceeded the set value ΔPa or ΔPb. The exhaust temperatureincreasing control device controls at least the operation amount of thesolenoid proportional valve 38 so that the increment of the absorptiontorque of the hydraulic pump 2 amounts to 20%-30% of the maximum torqueof the engine 1.

The processing function of the controller 20 in the steps S305-S350 inFIG. 6 and the steps S405-S450 in FIG. 7 forms an automatic recoverycontrol device which automatically starts operation when the exhaustresistance detected by the exhaust resistance sensor 34 has reached orexceeded the set value ΔPa.

The switch 13 forms operation permission state detecting means whichdetects whether the hydraulic operating machine is in the operationpermission state or not. The manual recovery switch 36 forms manualrecovery instruction means. The manual recovery instruction means andthe processing function of the controller 20 in the steps S500-S610 inFIG. 8 form a manual recovery control device which issues an alarm whenthe exhaust resistance detected by the exhaust resistance sensor 34 hasreached or exceeded the set value ΔPb and starts operation when theswitch 13 (operation permission state detecting means) detects that thehydraulic operating machine is not in the operation permission state andthere is an instruction by (received through) the manual recovery switch36 (manual recovery instruction means).

In this embodiment configured as above, even when the atmospherictemperature as operating environment of the hydraulic operating machinechanges in a wide range (e.g., −30° C.-40° C.) and the exhaust gastemperature changes correspondingly, the exhaust gas temperature isincreased by operating the solenoid proportional valve 38 so that theexhaust gas temperature as the output value of the exhaust temperaturesensor 33 reaches the preset value Ta. Therefore, the recovery processof the exhaust gas purification device can be executed with reliabilityby increasing the exhaust gas temperature irrespective of the operatingenvironment and economic efficiency can be improved by keeping the fuelconsumption at a minimum necessary level.

Further, the present inventors have confirmed that the exhaust gastemperature can be increased to approximately 250° C.-350° C. withoutcausing any problem to the operation of the hydraulic operating machinedriving hydraulic actuators if the hydraulic absorption torque generatedby a hydraulic absorption torque increasing device is approximately20%-30% of the aforementioned maximum engine torque. By controlling theoperation amount of the solenoid proportional valve 38 so that theincrement of the absorption torque of the hydraulic pump 2 amounts to20%-30% of the maximum torque of the engine 1, unnecessary and excessiveincrease in the exhaust gas temperature can be avoided, the fuelconsumption can be kept at a minimum necessary level, and the economicefficiency can be improved. Furthermore, even in the operating state,the filter recovery process can be performed by increasing the exhaustgas temperature without causing any problem to the operation of themachine. Consequently, working efficiency can be increased through theimprovement of workability during the execution of the recovery controland the reduction of the operation interruption frequency of themachine.

In any type of recovery control (the automatic recovery control in theoperating state, the automatic recovery control in the non-operatingstate, the manual recovery control), the filter recovery process can beperformed reliably by increasing the exhaust gas temperature and thefuel consumption can be kept at a minimum necessary level irrespectiveof the operating environment.

In the case where the exhaust resistance set value in the automaticrecovery control for cases where the hydraulic actuator 25 is not beingdriven is set at the value ΔPd lower than the exhaust resistance setvalue ΔPa for cases where the hydraulic actuator 25 is being driven, thefollowing effect is achieved: In the non-operating state (i.e., when nohydraulic actuator is being driven) in which the exhaust gas temperatureis relatively low and the particulate matter (PM) tends to accumulaterelatively more, the PM accumulated on the filter of the exhaust gaspurification device 32 can be combusted more frequently than in theoperating state (i.e., when a hydraulic actuator is being driven) andthe filter of the exhaust gas purification device 32 can be recoveredefficiently.

Moreover, since the set value ΔPa for the automatic recovery control isset lower than the set value ΔPb for the manual recovery control, thefrequency of the automatic recovery control increases and the frequencyof the manual recovery control decreases due to the output value of theexhaust resistance sensor 34 increasing to the set value ΔPb lessfrequently. This also contributes to the reduction of the operationinterruption frequency of the hydraulic operating machine.

In addition, in the automatic recovery control in the operating state,the exhaust resistance threshold value ΔPa for judging whether theautomatic recovery control is necessary or not and the exhaustresistance threshold value ΔPc for judging whether the recovery controlshould be ended or not are determined and set through the aforementionedcalculation. Therefore, appropriate threshold values ΔPa and ΔPcincorporating the operating status of the engine can be set and therecovery control can be executed properly.

A second embodiment in accordance with the present invention will bedescribed below with reference to FIGS. 13-16. In this embodiment, thepump torque control is executed directly by the regulator without usingthe controller.

FIG. 13 is a schematic diagram showing a hydraulic driving system of ahydraulic operating machine equipped with an exhaust gas purificationsystem in accordance with the second embodiment, wherein elementsequivalent to those shown in FIG. 1 are assigned the same referencecharacters. In FIG. 13, the hydraulic driving system of this embodimentis equipped with a controller 20A, a regulator 14A to which thedischarge pressure of the hydraulic pump 2 is lead via a hydraulic line41, and a solenoid proportional valve 42 which operates according to acontrol signal from the controller 20A and outputs control pressurespecifying the target tilting angle qr of the hydraulic pump 2 to theregulator 14A.

When the hydraulic actuator 25 is operated, the controller 20A detectsthe operation amount of the control lever device 8 and the enginerevolution speed at that time with the pressure sensor 16 and therevolution sensor 18, respectively, calculates the target tilting angleof the hydraulic pump 2 through a calculation process for the positivecontrol, and outputs a control signal to the solenoid proportional valve42 so that the target tilting angle is achieved. The solenoidproportional valve 42 outputs control pressure corresponding to thecontrol signal. The regulator 14A changes the tilting angle of thehydraulic pump 2 according to the control pressure.

FIG. 14 is a flow chart showing the contents of a calculation processfor the positive control of the hydraulic pump 2 executed by thecontroller 20A, wherein steps identical with those in FIG. 2 areassigned the same reference characters. As is clear from the comparisonbetween FIGS. 2 and 14, the controller 20A in this embodiment isconfigured to execute only the steps S10, S15 and S30 related to thepositive control. In the step S30, the controller 20A outputs thecontrol signal for achieving the target tilting angle qr to the solenoidproportional valve 42.

The regulator 14A is configured to execute the positive control based onthe output pressure (control pressure) of the solenoid proportionalvalve 42 while also executing the pump torque control by itself based onthe discharge pressure of the hydraulic pump 2 supplied via thehydraulic line 41. Specifically, when the control pressure outputted bythe solenoid proportional valve 42 changes, the regulator 14A controlsthe tilting angle of the hydraulic pump 2 so that the target tiltingangle qr specified by the control pressure is achieved (positivecontrol). Further, when the discharge pressure of the hydraulic pump 2increases and the target tilting angle qr specified by the controlpressure reaches or exceeds the maximum tilting angle qmax for the pumptorque limiting control, the regulator 14A controls the tilting angle ofthe hydraulic pump 2 so as to limit the tilting angle to the maximumtilting angle qmax (pump torque limiting control or pump horsepowercontrol). Such a regulator 14A is publicly known.

FIG. 15 is a graph like FIG. 3 showing the absorption torque property ofthe hydraulic pump 2 acquired as a result of the pump torque limitingcontrol, wherein the horizontal axis represents the discharge pressurePp of the hydraulic pump 2 and the vertical axis represents the tiltingangle (displacement) q of the hydraulic pump 2.

In FIG. 15, the absorption torque property of the hydraulic pump 2 ismade up of a constant maximum tilting angle property line Tp0 andconstant maximum absorption torque property lines Tp2 and Tp3. Thecontrol of the tilting angle of the hydraulic pump 2 when the dischargepressure P of the hydraulic pump 2 is under the first value P0 (on theconstant maximum tilting angle property line Tp0) is identical with thatin FIG. 3. As the discharge pressure P of the hydraulic pump 2 increasesover the first value P0, the maximum tilting angle qmax of the hydraulicpump 2 decreases along the constant maximum absorption torque propertylines Tp2 and Tp3 and the absorption torque of the hydraulic pump 2 iskept at maximum torque Tmax which is determined by the property linesTp2 and Tp3. The constant maximum absorption torque property lines Tp2and Tp3 have been set based on two springs installed in the regulator14A. Each property line Tp2, Tp3 is in a shape imitating a hyperboliccurve. The maximum torque Tmax determined by the property lines Tp2 andTp3 has been set slightly lower than limit torque TEL of the engine 1.With this setting, when the discharge pressure P of the hydraulic pump 2increases over the first value P0, the absorption torque (input torque)of the hydraulic pump 2 is controlled so as not to exceed the presetmaximum torque Tmax (so as not to exceed the limit torque TEL of theengine 1) by decreasing the maximum tilting angle qmax of the hydraulicpump 2.

FIG. 16 is a flow chart showing the details of the hydraulic absorptiontorque increasing control in the step S312 in FIG. 6 regarding theautomatic recovery control in the operating state, wherein stepsidentical with those in FIG. 11 are assigned the same referencecharacters. As is clear from the comparison between FIGS. 11 and 16, thecalculation process for the positive control executed by the controller20A is invalidated in step S60A and validated in step S70A since thecontroller 20A in this embodiment executes the calculation process forthe positive control only. The details of the hydraulic absorptiontorque increasing control in the step S412 in FIG. 7 regarding theautomatic recovery control in the non-operating state and the details ofthe hydraulic absorption torque increasing control in the step S545 inFIG. 8 regarding the manual recovery control executed when the machineis in the operation prohibition state are no different from those inFIG. 12 in the first embodiment.

According to this embodiment, effects similar to those of the firstembodiment can be achieved in hydraulic operating machines in which thepump torque control is executed directly by a regulator 14A.

A third embodiment in accordance with the present invention will bedescribed below with reference to FIGS. 17-19. This embodimentillustrates another example of the exhaust gas temperature increasingcontrol. FIG. 17 is a flow chart showing the contents of the automaticrecovery control in the operating state. FIG. 18 is a flow chart showingthe contents of the automatic recovery control in the non-operatingstate. FIG. 19 is a flow chart showing the contents of the manualrecovery control when the hydraulic operating machine is in theoperation prohibition state. FIGS. 17-19 correspond to FIGS. 6-8 in thefirst embodiment, respectively.

In the first and second embodiments, only the recovery control(additional fuel injection) is executed and no fine adjustment of theexhaust gas temperature T is made after the exhaust gas temperature Thas been raised to the threshold value Ta by the exhaust gas temperatureincreasing control. In this embodiment, the exhaust gas temperature T isadjusted to be within a prescribed temperature range with respect to thethreshold value Ta even after the exhaust gas temperature T hasreached/exceeded the threshold value Ta due to the exhaust gastemperature increasing control, by meticulously performing the hydraulicabsorption torque increasing control and/or the engine revolution speedincreasing control.

Specifically, after executing the exhaust gas temperature increasingcontrol (hydraulic absorption torque increasing control) in the stepS312 in FIG. 17, the controller 20A judges whether the exhaust gastemperature T in the exhaust gas purification device 32 is within apreset temperature range between reference temperatures Ta1 and Ta2 ornot based on the output value of the exhaust temperature sensor 33 (stepS365). When the exhaust gas temperature T is within the presettemperature range, the controller 20A starts the recovery control(additional fuel injection) (step S320). When the exhaust gastemperature T is not within the preset temperature range, the controller20A adjusts the torque increment of the hydraulic absorption torqueincreasing control (step S370) and repeats the torque incrementadjustment until the exhaust gas temperature T comes within the presettemperature range (step S365→S370).

Here, the reference temperatures Ta1 and Ta2 specifying the presettemperature range satisfy a relationship Ta1<Ta2. The referencetemperature Ta1 may be set equal to the threshold value Ta in the firstand second embodiments, for example. The reference temperature Ta2 isset slightly (e.g., 5° C.-50° C. (preferably, about 10° C.-30° C.))higher than Ta1.

The torque increment adjustment in the hydraulic absorption torqueincreasing control is made by increasing/decreasing at least one of thetarget tilting angle qco and the target pressure Pco for the hydraulicabsorption torque increasing control by a prescribed amount when thetarget tilting angle qr for the positive control is less than or equalto the target tilting angle qco for the hydraulic absorption torqueincreasing control. When the target tilting angle qr for the positivecontrol is greater than the target tilting angle qco for the hydraulicabsorption torque increasing control, the torque increment adjustment inthe hydraulic absorption torque increasing control is made byincreasing/decreasing the target pressure Pco for the hydraulicabsorption torque increasing control by a prescribed amount in order toavoid ill effect on the positive control. By increasing/decreasing thetarget tilting angle qco by a prescribed amount, the operation amount ofthe regulator 14 is controlled and the tilting angle (displacement) ofthe hydraulic pump 2 is adjusted. By increasing/decreasing the targetpressure Pco by a prescribed amount, the operation amount (opening area)of the solenoid proportional valve 38 is controlled and the dischargepressure of the hydraulic pump 2 is adjusted. Therefore, byincreasing/decreasing at least one of the target tilting angle qco andthe target pressure Pco by a prescribed amount, the absorption torque ofthe hydraulic pump 2 is controlled and the engine load isincreased/decreased, by which the exhaust gas temperature can beadjusted.

Also in the steps S465 and S470 in FIG. 18 and the steps S665 and S670in FIG. 19, a process substantially identical with that of the stepsS365 and S370 in FIG. 17 is executed. However, it is unnecessary toconsider the ill effect on the positive control in FIGS. 18 and 19(control in the non-operating state). Thus, the torque incrementadjustment in the hydraulic absorption torque increasing control in thesteps S470 and S670 may be made constantly by increasing/decreasing atleast one of the target tilting angle qco and the target pressure Pcofor the hydraulic absorption torque increasing control by a prescribedamount. Incidentally, the adjustment of the exhaust gas temperaturedescribed above may be made also by increasing/decreasing the enginerevolution speed in the engine revolution speed increasing control incombination with or in place of the torque increment adjustment in thehydraulic absorption torque increasing control.

In the above explanation, the processing function of the controller 20Ain the steps S305-S350, S365 and S370 in FIG. 17, the steps S405-S450,S465 and S470 in FIG. 18, and the steps S500-S610, S665 and S670 in FIG.19 forms a recovery control device which executes the recovery of theexhaust gas purification device 32 by combusting and removing theparticulate matter accumulated in the exhaust gas purification device 32when the exhaust resistance detected by the exhaust resistance sensor 34has reached or exceeded the set value ΔPa or ΔPb.

The processing function of the controller 20A in the steps S312, S365and S370 in FIG. 17, the steps S412, S465 and S470 in FIG. 18 and thesteps S545, S665 and S670 in FIG. 19 forms an exhaust temperatureincreasing control device which increases the exhaust gas temperature soas to make the exhaust gas temperature detected by the exhausttemperature sensor 33 reach a preset value by increasing the absorptiontorque of the hydraulic pump 2 by operating at least the latter one(solenoid proportional valve 38) of the regulator 14 (pump displacementadjusting device) and the solenoid proportional valve 38 (pump dischargepressure increasing device) when the exhaust resistance detected by theexhaust resistance sensor 34 has reached or exceeded the set value ΔPaor ΔPb.

The steps S365 and S370 (FIG. 17), the steps S465 and S470 (FIG. 18) andthe steps S665 and S670 (FIG. 19) form an exhaust temperature adjustingdevice which adjusts at least one selected from the operation amount ofthe regulator 14 or 14A (pump displacement adjusting device), theoperation amount of the solenoid proportional valve 38 (pump dischargepressure increasing device) and the increment of the engine revolutionspeed so that the exhaust gas temperature remains within a preset rangeTa1-Ta2 after the exhaust gas temperature detected by the exhausttemperature sensor 33 has been increased to the preset value Ta1.

In this embodiment configured as above, the torque increment in thehydraulic absorption torque increasing control and/or the increment ofthe engine revolution speed in the engine revolution speed increasingcontrol is finely adjusted so that the exhaust gas temperature T remainswithin the preset temperature range. Therefore, the exhaust gastemperature T can be reliably controlled and kept within the presettemperature range. Consequently, ill effect on the operation can beminimized in the recovery control in the operating state. In therecovery control in the non-operating state, unnecessary increase in theengine load can be avoided and the fuel consumption can be kept at aminimum necessary level irrespective of the operating environment, bywhich the economic efficiency can be improved further.

Incidentally, while the fuel injection for the recovery control in theabove embodiments is executed by means of the post-injection (additionalinjection) in the expansion stroke after the main injection of theengine, the fuel injection for the recovery control may also be carriedout by providing the exhaust line with an extra fuel injection devicefor the recovery control and operating the fuel injection device.

While the hydraulic absorption torque increasing control in the aboveembodiments is executed by providing the solenoid proportional valve 38(for exerting the load for increasing the exhaust gas temperature on theengine in the recovery control) in the discharging hydraulic line 2 a ofthe hydraulic pump 2 and controlling the operation amount (opening area)of the solenoid proportional valve 38, the solenoid proportional valve38 may also be placed at the downstream end of a center bypass hydraulicline penetrating the flow/directional control valve 4. Further, theexertion of the load on the engine may also be implemented by use ofdifferent means.

While the present invention has been applied to a hydraulic shovel as anexample of a hydraulic operating machine in the above embodiments, thepresent invention may of course be applied to hydraulic operatingmachines other than hydraulic shovels (wheel shovels, crane trucks,etc.). Also in such cases, effects similar to those of the aboveembodiments can be achieved.

DESCRIPTION OF REFERENCE NUMERALS

-   1 engine-   1 a electronic governor-   2 main hydraulic pump-   2 a discharging hydraulic line-   3 pilot pump-   4, 5 flow/directional control valve-   8 control lever device-   8 a, 8 b pilot valve-   9 main relief valve-   10 pilot relief valve-   11 pilot cut valve-   12 safety lever (gate lock lever)-   13 switch-   14, 14A regulator-   16 pressure sensor-   17 pressure sensor-   18 revolution sensor-   19 engine control dial-   20, 20A controller-   21 a, 21 b shuttle valve-   25 hydraulic actuator-   31 exhaust line-   32 exhaust gas purification device-   33 exhaust temperature sensor-   34 exhaust resistance sensor-   36 manual recovery switch-   37 alarm lamp-   38 solenoid proportional valve (hydraulic absorption torque    increasing device)-   41 hydraulic line-   42 solenoid proportional valve

1. An exhaust gas purification system for a hydraulic operating machineequipped with a diesel engine (1), an exhaust gas purification device(32) provided in an exhaust line (31) of the engine, a variabledisplacement hydraulic pump (2) driven by the engine, a pumpdisplacement adjusting device (14, 14A) for controlling the displacementof the hydraulic pump, and at least one hydraulic actuator (25) drivenby hydraulic fluid discharged from the hydraulic pump, comprising: anexhaust resistance sensor (34) for detecting exhaust resistance of theexhaust gas purification device (32); an exhaust temperature sensor (33)for detecting temperature of exhaust gas in the exhaust gas purificationdevice; a pump discharge pressure increasing device (38) provided in ahydraulic line (2 a), through which the hydraulic fluid discharged fromthe hydraulic pump (2) flows, for increasing discharge pressure of thehydraulic pump; and a recovery control device (20, 20A) for executingrecovery of the exhaust gas purification device by combusting andremoving particulate matter accumulated in the exhaust gas purificationdevice when the exhaust resistance detected by the exhaust resistancesensor has reached or exceeded a set value, wherein the recovery controldevice includes an exhaust temperature increasing control device (20,20A) which increases the exhaust gas temperature so as to make theexhaust gas temperature detected by the exhaust temperature sensor reacha preset value by increasing absorption torque of the hydraulic pump byoperating at least the latter one of the pump displacement adjustingdevice (14, 14A) and the pump discharge pressure increasing device (38)when the exhaust resistance detected by the exhaust resistance sensorhas reached or exceeded the set value.
 2. The exhaust gas purificationsystem for a hydraulic operating machine according to claim 1, whereinthe exhaust temperature increasing control device (20, 20A) controls anoperation amount of at least the latter one of the pump displacementadjusting device (14, 14A) and the pump discharge pressure increasingdevice (38) so that an increment of the absorption torque of thehydraulic pump (2) amounts to 20%-30% of maximum torque of the engine(1).
 3. The exhaust gas purification system for a hydraulic operatingmachine according to claim 1, wherein the exhaust temperature increasingcontrol device (20,20A) includes an exhaust temperature adjusting devicewhich adjusts at least one selected from an operation amount of the pumpdisplacement adjusting device (14, 14A), an operation amount of the pumpdischarge pressure increasing device (38) and an increment of revolutionspeed of the engine so that the exhaust gas temperature remains within apreset range after the exhaust gas temperature detected by the exhausttemperature sensor (33) has been increased to the preset value.
 4. Theexhaust gas purification system for a hydraulic operating machineaccording to claim 1, wherein the recovery control device is anautomatic recovery control device (20, 20A) which automatically startsoperation when the exhaust resistance detected by the exhaust resistancesensor has reached or exceeded the set value.
 5. The exhaust gaspurification system for a hydraulic operating machine according to claim4, further comprising operation detecting means for detecting whetherthe hydraulic actuator (25) is being driven or not, wherein the exhausttemperature increasing control device (20, 20A) increases the exhaustgas temperature by increasing the absorption torque of the hydraulicpump by operating at least the latter one of the pump displacementadjusting device (14, 14A) and the pump discharge pressure increasingdevice (38) when the hydraulic actuator (25) is being driven.
 6. Theexhaust gas purification system for a hydraulic operating machineaccording to claim 5, wherein when the hydraulic actuator (25) is notbeing driven, the exhaust temperature increasing control device (20,20A) increases the exhaust gas temperature by increasing revolutionspeed of the engine to a preset revolution speed and increasing theabsorption torque of the hydraulic pump (2) by operating the pumpdisplacement adjusting device (14, 14A) and the pump discharge pressureincreasing device (38).
 7. The exhaust gas purification system for ahydraulic operating machine according to claim 1, further comprising:operation permission state detecting means (13) for detecting whetherthe hydraulic operating machine is in an operation permission state ornot; and manual recovery instruction means (36), wherein: the recoverycontrol device is a manual recovery control device (36, 20, 20A) whichissues an alarm when the exhaust resistance detected by the exhaustresistance sensor (34) has reached or exceeded the set value and startsoperation when the operation permission state detecting means detectsthat the hydraulic operating machine is not in the operation permissionstate and there is an instruction by the manual recovery instructionmeans, and the exhaust temperature increasing control device (20, 20A)increases the exhaust gas temperature by increasing revolution speed ofthe engine to a preset revolution speed and increasing the absorptiontorque of the hydraulic pump (2) by operating the pump displacementadjusting device (14, 14A) and the pump discharge pressure increasingdevice (38).
 8. The exhaust gas purification system for a hydraulicoperating machine according to claim 4, wherein the exhaust temperatureincreasing control device (20, 20A) previously stores an exhaustresistance threshold value, for judging whether the recovery of theexhaust gas purification device by the automatic recovery control device(20, 20A) is necessary or not, as a function of engine revolution speedand an engine load, determines the exhaust resistance threshold value byreferring to current engine revolution speed and engine load andinputting them to the function, and sets the determined exhaustresistance threshold value as the set value.
 9. The exhaust gaspurification system for a hydraulic operating machine according to claim4, wherein the automatic recovery control device (20, 20A) sets the setvalue of the exhaust resistance at a lower value when the hydraulicactuator is not being driven compared to cases where the hydraulicactuator is being driven.
 10. The exhaust gas purification system for ahydraulic operating machine according to claim 1, wherein: the recoverycontrol device includes an automatic recovery control device (20, 20A)which automatically starts operation when the exhaust resistancedetected by the exhaust resistance sensor has reached or exceeded theset value and a manual recovery control device (36, 20, 20A) whichissues an alarm when the exhaust resistance detected by the exhaustresistance sensor (34) has reached or exceeded the set value and startsoperation when the operation permission state detecting means detectsthat the hydraulic operating machine is not in the operation permissionstate and there is an instruction by the manual recovery instructionmeans, and the set value in the automatic recovery control device (20,20A) is set lower than the set value in the manual recovery controldevice (36, 20, 20A).